We have been studying the pokeweed mitogen (PWM)-induced differentiation of human peripheral blood B lymphocytes. In this culture system, T cells are required. Furthermore, PWM activates functionally distinct subsets of T cells, including helper, suppressor, and inducer, for T-T-cell interactions. Although these activated subsets carry the shared marker detected by the monoclonal antibody OKT4, reagents for distinguishing these functionally heterogeneous, T-cell subsets are not available. Since it is difficult to define and characterize the functions of these T-cell subsets without separation, we intend to analyze T-cell subsets through the use of selective cloning techniques. Our plans are to: (1)\clone proliferating T cells using a limiting dilution or micromanipulation method; (2)\functionally characterize cloned T cells in terms of their reactivity to PWM and autologous HLA-DR antigen, their ability to help or suppress B-cell differentiation, and their ability to affect the effector function of other T-cell subsets with distinct immunological functions; and (4)\analyze functions of peripheral blood T-cell subsets using monoclonal antibodies in PWM-induced polyclonal and antigen-induced antibody responses. The results of this investigation will provide detailed insight into the regulatory interactions between T and B cells that ultimately drive B cells into Ig-secreting cells. In the future, monoclonal antibodies which distinguish T-cell subsets will be invaluable reagents to investigate T-cell anomalies in various forms of immunodeficiency diseases and malignancies of lymphoid cell origin. (LB)